Year	% of total
1971	42.73537063238965
1972	39.499577477763495
1973	40.75846106581174
1974	37.34462279233297
1975	39.4018812304959
1976	38.174721181127566
1977	39.39037687366942
1978	44.416053948342224
1979	42.25240714589526
1980	40.80888866246105
1981	39.47899511828577
1982	36.31521381795475
1983	35.45813887105581
1984	34.67700738543252
1985	30.57234974235467
1986	29.722317870985666
1987	25.178170846364278
1988	27.023257052352513
1989	26.088428560423804
1990	27.057114925018368
1991	25.475584142988456
1992	23.692341741651116
1993	22.14837192436766
1994	24.01674206268749
1995	20.264015599664926
1996	18.105915705540124
1997	18.256594042953314
1998	18.723882088218346
1999	16.65259868695802
2000	14.540183954186258
2001	14.21885337940414
2002	13.35918392129766
2003	14.834918690949692
2004	15.045599885406896
2005	16.998503672374664
2006	17.387889558194843
2007	16.871394164673823
2008	15.297751629415263
2009	13.84719721054706
2010	14.429703993164594
2011	14.591822546381636
2012	12.502154778626155
2013	13.851002932337867
2014	12.422320385201585
2015	11.48858622630512